Question

我有几个字符串，我需要使用NumberFormat作为Double。字符串可以有多种格式，如下所示：

"0"           // case 1
"0.00003"     // case 2
"5e-76"       // case 3
"2E-10"       // case 4

我使用以下代码来获取double值：

    NumberFormat numberFormat = NumberFormat.getInstance(Locale.US);
    String val = "2e-7";
    try {
        Number number = numberFormat.parse(val);
        System.out.println("number: " + number.doubleValue());
    } catch (ParseException ex) {
        System.out.println("error: " + ex);
    }

除了案例3（运行上面的代码将打印“number：2.0”）

之外，这种方法很好

要求：

我知道Double.valueOf(val)在这里可以正常工作，但是我正在寻找仅使用NumberFormat的解决方案。

有可能实现这个目标吗？

Answer 1

案例3失败，因为“e”是小写的。我们可以创建一个NumberFormat的子类，在解析它之前将其置于字符串上面。

SYSMAP  System.map
DTC     arch/arm64/boot/dts/15801_DVT/msm8996-v3-pmi8996-mtp_15801_DVT.dtb
DTC     arch/arm64/boot/dts/15801_PVT/msm8996-v3-pmi8996-mtp_15801_PVT.dtb
DTC     arch/arm64/boot/dts/15811_PVT/msm8996pro-pmi8996-mtp_15811_PVT.dtb
DTC     arch/arm64/boot/dts/15811_PVT/msm8996pro-v1.1-pmi8994-mtp_15811_PVT.dtb
DTC     arch/arm64/boot/dts/15811_PVT2/msm8996pro-pmi8996-mtp_15811_PVT2.dtb
DTC     arch/arm64/boot/dts/15811_PVT2/msm8996pro-v1.1-pmi8994-mtp_15811_PVT2.dtb
DTC     arch/arm64/boot/dts/15811_PVT3/msm8996pro-pmi8996-mtp_15811_PVT3.dtb
DTC     arch/arm64/boot/dts/15811_PVT3/msm8996pro-v1.1-pmi8994-mtp_15811_PVT3.dtb
OBJCOPY arch/arm64/boot/Image
GZIP    arch/arm64/boot/Image.gz
DTC     arch/arm64/boot/dts/15811_PVT3/msm8996pro-v1.1-pmi8994-mtp_15811_PVT3.dtb
DTC     arch/arm64/boot/dts/15811_PVT3/msm8996pro-pmi8996-mtp_15811_PVT3.dtb
DTC     arch/arm64/boot/dts/15811_PVT/msm8996pro-v1.1-pmi8994-mtp_15811_PVT.dtb
DTC     arch/arm64/boot/dts/15811_PVT/msm8996pro-pmi8996-mtp_15811_PVT.dtb
DTC     arch/arm64/boot/dts/15801_PVT/msm8996-v3-pmi8996-mtp_15801_PVT.dtb
DTC     arch/arm64/boot/dts/15801_DVT/msm8996-v3-pmi8996-mtp_15801_DVT.dtb
DTC     arch/arm64/boot/dts/15811_PVT2/msm8996pro-pmi8996-mtp_15811_PVT2.dtb
DTC     arch/arm64/boot/dts/15811_PVT2/msm8996pro-v1.1-pmi8994-mtp_15811_PVT2.dtb
CAT     arch/arm64/boot/Image.gz-dtb
Building modules, stage 2.
MODPOST 1 modules
CC      drivers/staging/qcacld-2.0/wlan.mod.o
LD [M]  drivers/staging/qcacld-2.0/wlan.ko

public final class CaseInsensitiveNumberFormat extends NumberFormat {
    private final NumberFormat mParent;
    private final Locale mLocale;

    public CaseInsensitiveNumberFormat(Locale locale) {
        mParent = NumberFormat.getInstance(locale);
        mLocale = locale;
    }

    @Override
    public final Number parse(String s, ParsePosition pos) {
        return mParent.parse(s.toUpperCase(mLocale), pos);   // <------
    }

    @Override
    public final StringBuffer format(double number, StringBuffer appendTo, FieldPosition pos) {
        return mParent.format(number, appendTo, pos);
    }

    @Override
    public final StringBuffer format(long number, StringBuffer appendTo, FieldPosition pos) {
        return mParent.format(number, appendTo, pos);
    }
}

从几个科学记数中获取数字

1 个答案: